Model-based estimates of risks of disease transmission and economic costs of seven injection devices in sub-Saharan Africa.
(73/1101)
OBJECTIVE: To investigate and compare seven types of injection devices for their risks of iatrogenic transmission of bloodborne pathogens and their economic costs in sub-Saharan Africa. METHODS: Risk assumptions for each device and cost models were constructed to estimate the number of new hepatitis B virus (HBV) and human immunodeficiency virus (HIV) infections resulting from patient-to-patient, patient-to-health care worker, and patient-to-community transmission. Costs of device purchase and usage were derived from the literature, while costs of direct medical care and lost productivity from HBV and HIV disease were based on data collected in 1999 in Cote d'Ivoire, Ghana, and Uganda. Multivariate sensitivity analyses using Monte Carlo simulation characterized uncertainties in model parameters. Costs were summed from both the societal and health care system payer's perspectives. FINDINGS: Resterilizable and disposable needles and syringes had the highest overall costs for device purchase, usage, and iatrogenic disease: median US dollars 26.77 and US dollars 25.29, respectively, per injection from the societal perspective. Disposable-cartridge jet injectors and automatic needle-shielding syringes had the lowest costs, US dollars 0.36 and US dollars 0.80, respectively. Reusable-nozzle jet injectors and auto-disable needle and syringes were intermediate, at US dollars 0.80 and US dollars 0.91, respectively, per injection. CONCLUSION: Despite their nominal purchase and usage costs, conventional needles and syringes carry a hidden but huge burden of iatrogenic disease. Alternative injection devices for the millions of injections administered annually in sub-Saharan Africa would be of value and should be considered by policy-makers in procurement decisions. (+info)
Genetic structure of human populations.
(74/1101)
We studied human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 populations. Within-population differences among individuals account for 93 to 95% of genetic variation; differences among major groups constitute only 3 to 5%. Nevertheless, without using prior information about the origins of individuals, we identified six main genetic clusters, five of which correspond to major geographic regions, and subclusters that often correspond to individual populations. General agreement of genetic and predefined populations suggests that self-reported ancestry can facilitate assessments of epidemiological risks but does not obviate the need to use genetic information in genetic association studies. (+info)
Human population genetic structure and inference of group membership.
(75/1101)
A major goal of biomedical research is to develop the capability to provide highly personalized health care. To do so, it is necessary to understand the distribution of interindividual genetic variation at loci underlying physical characteristics, disease susceptibility, and response to treatment. Variation at these loci commonly exhibits geographic structuring and may contribute to phenotypic differences between groups. Thus, in some situations, it may be important to consider these groups separately. Membership in these groups is commonly inferred by use of a proxy such as place-of-origin or ethnic affiliation. These inferences are frequently weakened, however, by use of surrogates, such as skin color, for these proxies, the distribution of which bears little resemblance to the distribution of neutral genetic variation. Consequently, it has become increasingly controversial whether proxies are sufficient and accurate representations of groups inferred from neutral genetic variation. This raises three questions: how many data are required to identify population structure at a meaningful level of resolution, to what level can population structure be resolved, and do some proxies represent population structure accurately? We assayed 100 Alu insertion polymorphisms in a heterogeneous collection of approximately 565 individuals, approximately 200 of whom were also typed for 60 microsatellites. Stripped of identifying information, correct assignment to the continent of origin (Africa, Asia, or Europe) with a mean accuracy of at least 90% required a minimum of 60 Alu markers or microsatellites and reached 99%-100% when >/=100 loci were used. Less accurate assignment (87%) to the appropriate genetic cluster was possible for a historically admixed sample from southern India. These results set a minimum for the number of markers that must be tested to make strong inferences about detecting population structure among Old World populations under ideal experimental conditions. We note that, whereas some proxies correspond crudely, if at all, to population structure, the heuristic value of others is much higher. This suggests that a more flexible framework is needed for making inferences about population structure and the utility of proxies. (+info)
How human immunodeficiency virus voluntary testing can contribute to tuberculosis control.
(76/1101)
Human immunodeficiency virus (HIV) is fueling the tuberculosis (TB) epidemic, particularly in sub-Saharan Africa. However, despite their close epidemiological links, the public health responses have largely been separate. WHO has set out a strategy to decrease the burden of HIV-related TB, comprising interventions against both TB and HIV. Voluntary counselling and testing (VCT) for HIV can link TB and HIV programme activities. The benefits of VCT for HIV to TB patients include referral for appropriate clinical care and support for those testing HIV-positive. Likewise, people attending a centre for VCT can benefit from TB screening: those found to be both HIV-positive and with active TB need referral for TB treatment; those without active TB should be offered TB preventive treatment with isoniazid. To explore how VCT for HIV can contribute to a more coherent response to TB, WHO is coordinating the ProTEST Initiative. The name "ProTEST" is derived from the Promotion of voluntary testing as an entry point for access to the core interventions of intensified TB case-finding and isoniazid preventive treatment. Other interventions may be added to provide finally a comprehensive range of HIV and TB prevention and care interventions. Under the ProTEST Initiative, pilot districts are establishing links between centres for VCT for HIV and TB prevention and care. This will pave the way for large-scale operationalization of the comprehensive range of interventions needed to control TB in settings with high HIV prevalence. (+info)
Transferring policies for treating sexually transmitted infections: what's wrong with global guidelines?
(77/1101)
The paper uses a case study of the development of syndromic management for treating sexually transmitted infections (STIs) and subsequent policies recommending worldwide use of syndromic management guidelines. These treatment policies emerged in the late 1970s from researchers and public health physicians working in sub-Saharan Africa where they had to treat large numbers of STIs in difficult circumstances. Syndromic management was initially developed in specific local epidemiological and resource situations. By the late 1980s, the World Health Organization had adopted syndromic management as policy, and began to promote it globally in the form of algorithms and training guidelines. Dissemination was assisted by the context of the rapid spread of HIV/AIDS and the apparent effectiveness of syndromic management for treating STIs and slowing the transmission of HIV/AIDS. In the mid 1990s, international donors interested in HIV control and women's reproductive health took it up, and encouraged national programmes to adopt the new guidelines. Implementation, however, was a great deal more complex than anticipated, and was exacerbated by differences between three rather separate policy networks involved in the dissemination and execution of the global guidelines. The analysis focuses on two parts of the process of policy transfer: the organic development of scientific and medical consensus around a new policy for the treatment of STIs; and the formulation and subsequent dissemination of international policy guidelines. Using a political science approach, we analyze the transition from clinical tools to global guidelines, and the associated debates that accompanied their use. Finally, we comment on the way current global guidelines need to be adapted, given the growth in knowledge. (+info)
Review of human immunodeficiency virus type 1-related opportunistic infections in sub-Saharan Africa.
(78/1101)
Understanding the natural history of human immunodeficiency virus type 1 (HIV-1) and opportunistic infections in sub-Saharan Africa is necessary to optimize strategies for the prophylaxis and treatment of opportunistic infections and to understand the likely impact of antiretroviral therapy. We undertook a systematic review of the literature on HIV-1 infection in sub-Saharan Africa to assess data from recent cohorts and selected cross-sectional studies to delineate rates of opportunistic infections, associated CD4 cell counts, and associated mortality. We searched the MEDLINE database and the Cochrane Database of Systematic Reviews and Cochrane Clinical Trials Register for English-language literature published from 1990 through April 2002. Tuberculosis, bacterial infections, and malaria were identified as the leading causes of HIV-related morbidity across sub-Saharan Africa. Of the few studies that reported CD4 cell counts, the range of cell counts at the time of diagnosis of opportunistic infections was wide. Policies regarding the type and timing of opportunistic infection prophylaxis may be region specific and urgently require further study. (+info)
Extensive female-mediated gene flow from sub-Saharan Africa into near eastern Arab populations.
(79/1101)
We have analyzed and compared mitochondrial DNA variation of populations from the Near East and Africa and found a very high frequency of African lineages present in the Yemen Hadramawt: more than a third were of clear sub-Saharan origin. Other Arab populations carried approximately 10% lineages of sub-Saharan origin, whereas non-Arab Near Eastern populations, by contrast, carried few or no such lineages, suggesting that gene flow has been preferentially into Arab populations. Several lines of evidence suggest that most of this gene flow probably occurred within the past approximately 2,500 years. In contrast, there is little evidence for male-mediated gene flow from sub-Saharan Africa in Y-chromosome haplotypes in Arab populations, including the Hadramawt. Taken together, these results are consistent with substantial migration from eastern Africa into Arabia, at least in part as a result of the Arab slave trade, and mainly female assimilation into the Arabian population as a result of miscegenation and manumission. (+info)
Malaria transmission in urban sub-Saharan Africa.
(80/1101)
The rapid increase in the world's urban population has major implications for the epidemiology of malaria. A review of malaria transmission in sub-Saharan African cities shows the strong likelihood of transmission occurring within these sprawling cities, whatever the size or characteristics of their bioecologic environment. A meta-analysis of results from studies of malaria transmission in sub-Saharan Africa shows a loose linear negative relationship between mean annual entomologic inoculation rates (EIR) and the level of urbanicity. Few studies have failed to find entomologic evidence of some transmission. Our results show mean annual EIRs of 7.1 in the city centers, 45.8 in periurban areas, and 167.7 in rural areas. The impact of urbanization in reducing transmission is more marked in areas where the mean rainfall is low and seasonal. Considerable variation in the level of transmission exists among cities and within different districts in the same city. This article presents evidence from past literature to build a conceptual framework to begin to explain this heterogeneity. The potential for malaria epidemics owing to decreasing levels of natural immunity may be offset by negative impacts of urbanization on the larval ecology of anopheline mosquitoes. Malaria control in urban environments may be simpler as a result of urbanization; however, much of what we know about malaria transmission in rural environments might not hold in the urban context. (+info)